FIELD OF THE INVENTION
The invention relates to an equalizing reservoir configuration for fluid circuits with volume and/or pressure fluctuations, especially for cooling circuits in nuclear power stations.
Open cooling circuits in nuclear power stations, such as intermediate cooling circuits in pressurized-water nuclear power stations, require equalizing reservoirs which can receive or discharge fluid, for absorbing fluctuations in the coolant volume, which result from operation. In order to prevent inadmissible pressure fluctuations in the system in such a case, on one hand the equalizing reservoirs must be connected to the atmosphere, in order to be able to "breathe" and, if necessary, ensure an overflow. On the other hand, however, direct access of the exterior air into the fluid present in the equalizing reservoir must be prevented, so that no chemical reactions with the exterior air and the cooling water in the reservoir can proceed. For reasons of corrosion protection, the cooling water generally contains hydrazine which might be degraded by carbon dioxide and atmospheric oxygen.
German Patent DE 29 51 458 C2 discloses an equalizing reservoir, especially for fluid circuits with volume fluctuations in nuclear power stations, which includes a fluid chamber. The latter is connected to the fluid circuit through a fluid line starting from the base of the reservoir. There is a gas chamber or a gas buffer chamber above the fluid chamber. The fluid chamber of the equalizing reservoir communicates with a fluid riser, which extends at least up to the maximum height of the upper side of the equalizing reservoir and contains a water/air seal. The fluid riser is bent, preferably in the form of an S. In other words, the upper end of the riser is formed in the shape of a U. That prevents dirt from dropping in and allows overflowing quantities of fluid to be caught.
The invention of the instant application begins from the realization that, in the known equalizing reservoir, the equalizing volume given by the fluid riser is still relatively small. Level monitoring of the equalizing reservoir is therefore relatively involved, because under all circumstances it must be avoided that the liquid riser is sucked dry in the event of pressure fluctuations in the direction of the reduced pressure and the level of the water seal in the equalizing reservoir thus falls. The fluid riser, which is bent in the shape of an S and which extends laterally and into a space above the reservoir, requires a relatively large absorption volume which is not always available in narrow interspaces in a nuclear power station.